This disclosure relates to new forms of metal powder and, in particular, to a new silver powder structure, one characterized by an extremely thin, flake-shaped structure. The powder is characterized by an ability to impart good electrically-conductive properties to silver-filled, organic-resin matrices at unprecedented low levels of filler loading.
It is already known in the art to provide silver flake materials for use as conductive powders in filling such organic resin-based matrix materials as polyolefins, polyester, acrylic resins, epoxy and polyurethane resins, polyvinyl chloride, silicone resins, and the like. Indeed silver flake materials are the silver particles of choice in most compositions wherein one wishes to minimize silver content while achieving high conductivity.
Silver flake use in such applications is prepared by mechanical means and has been characterized by some contamination by lubricants such as fatty acids used in a flake-forming step and, it is supposed, by some morphological changes associated with work-hardening of the silver during the flake-formation process.
Applicant set out to provide alternate forms of silver flake in the hope that one or more drawbacks of the present flake might be avoided.